1. Field of the Invention
The present invention relates to conveying devices of which the components are linked together such that the distance between them varies as a function of velocity.
2. Description of the Prior Art
A stretchable bandconveyor is a bandconveyor made of a succession of elements sliding into or above each other and linked to each other by devices for varying the distance between them such that the visible length and the speed of the elements vary along their course.
A stretchable train of cars is an endless succession of cars linked to each other by devices varying the distance between them.
A stretchable and endless train of cars may be used in combination with bandconveyors at loading/unloading stations where the speed of the cars and the distance between them is at a minimum and is synchronized over some distance with the speed of the bandconveyors in order to enable people to go from the bandconveyors to the cars and vice versa.
Several variable speed bandconveyors are known in the prior art. One such device uses components which are longer than they are wide. These components slide along each other, while the relative direction of motion progressively changes from a direction perpendicular to the long side of the components to a direction parallel to it, and therefore, the speed of the components varies proportionally to the ratio of their length and width. Another example of a rotating type conveying apparatus is illustrated in U.S. Pat. No. 3,485,182. In another existing device components are driven by a single threaded rod with variable pitch.
Bandconveyors which operate at constant speeds and which are used to go into or out of cars moving at the same speed are also known in the art. Usually, those cars are attached to a cable moving at constant speed, and the distance between them is fixed. These prior art devices do not utilize controllable means for coupling the components and/or cars to achieve variable speed and variable distance operation while maintaining the components aligned, i.e. unrotated, with respect to the closed-loop path followed by the components.
Other known systems use means to control the bandconveyors but they are limited to configurations where the elements of the bandconveyors do not slide within one another or where the elements rotate perpendicularly to the direction of movement.
For instance, the device disclosed in U.S. Pat. No. 3,881,423 and French Pat. No. 2,345,329 use cables for connecting cars. However, the winding or stretching means of the cables utilize devices such as a take-up reel to control the cable lengths and moreover are not applicable to elements of a stretchable bandconveyor where the elements slide within one another.
Swiss Pat. No. 397,999 uses articulated rods for connecting elements sliding above each other as opposed to within one another. This limits the device to expansion ratios of no more than 2 to 1 without having the components rotate because of their geometry. U.S. Pat. Nos. 4,053,044 and 3,834,520 and 3,462,002 are similar to Swiss Pat. No. 397,999 but they use cables instead of articulated rods. Like the device of Swiss No. 397,999, these devices are not applicable to stretchable conveyors where the elements slide within one another.
U.S. Pat. No. 4,370,932 hereby incorporated by reference, details a transportation using a closed-loop path and a mechanism for controlling the speed of the land carrying components and their distance apart. The mechanism moves the load carrying compounds along a closed loop path without rotation of the components in a direction traversed to the closed loop path.